The International Communist Party (ICP) is a left communist international political party which is often described by outside observers as Bordigist, due to the contributions by longtime member Amadeo Bordiga. The strongest base of the ICP remains Italy, where it was founded, but the Party also has sections in other countries.

A clearly left current, the Sinistra, emerged at the Italian Socialist Party’s (PSI) Congress of Milan in opposition to the reformist leadership of the party and the trade unions, and soon took a leading position in labor struggles. This Left, the Sinistra, made clear its internationalism by strongly opposing the Italo-Turkish War (1911), and organized itself nationally as the Intransigent Revolutionary Faction at the Reggio Emilia Congress of 1912. A similar conflict broke out in the Socialist Youth Federation against those who wanted the body to become largely a culture-dispensing organization. By the Sinistra, both party and Young Federation were seen as organs of struggle. The militant youth were to receive their revolutionary inspiration and stamina from the whole life and experience of the party as it guided the working class on the road to revolution, and not from some banal “party school” education. Amadeo Bordiga (1889–1970) and the “Revolutionary Socialist Club Carlo Marx” of Naples were decisive influences amongst the Intransigent Revolutionaries, and have remained fundamental references points in the history of the Sinistra.

With World War I the Sinistra proclaimed the need for revolutionary defeatism, which was in full agreement with Vladimir Lenin’s theses, hardly known at the time in Italy. With a background tragically highlighted by the failure to oppose the war when most Socialist parties voted war credits and solidified with their respective national bourgeoisie, the PSI, notwithstanding the efforts by the Sinistra, approved an ambiguous slogan, “neither support nor sabotage,” which meant no support for the war, but no fight against it either. With Benito Mussolini at their head, the interventionists had earlier abandoned the party.

At the outbreak of the October Revolution, the Sinistra aligned itself unhesitatingly with Lenin and Leon Trotsky, greeting the event as the opening phase of an international revolution. “Bolshevism, A Plant for Every Clime” was the piece written by Bordiga which warmly greeted the revolution. Antonio Gramsci and Palmiro Togliatti, who would form the group publishing L’Ordine Nuovo in 1919, were initially under the influence of a non-Marxist idealism and displayed a somewhat confused and ambiguous understanding of the event. In the article “The Revolution Against ‘Capital’,” Gramsci expressed the opinion that the October Revolution negated Marxist materialism. In Italy, the Sinistra, the only faction in the PSI with a national network, was able to convoke the party to a meeting in Florence in 1917 that led to the reaffirmation of intransigent opposition to the war. Beginning in 1918, with the nation seized by mounting social tensions resulting from the war and indicated by the increasing strikes and malcontent, the Sinistra, in possession of its own organ, Il Soviet, from December of that year, took the lead in getting the PSI to support revolutionary Russia and openly recognize the international significance of Lenin’s strategy.

This was the crucial year for all of Europe: the year of the great strikes in Italy and revolutionary attempts in Germany and Hungary, the year Rosa Luxemburg and Karl Liebknecht were massacred, and the year of the birth of the Third International as the party of the world revolution. In Italy, a polemic broke out between the Sinistra - pressing for the creation of an authentic communist party able to apply the experience of the Russian October Revolution to the West and stressing the social and political novelty of the soviet as an organ of sovereign power in the revolutionary process-and Gramsci’s L’Ordine Nuovo, that insisted in identifying the factory council as the equivalent of the soviet, portraying the council-normatively a subsidiary organ operating within the social and political functions of capitalism-as “the embryo of the future society.” Still in 1919, thanks to the theoretical and practical actions of the Sinistra, a Communist Abstentionist faction was founded in the PSI, the nucleus of the future Communist Party of Italy (Partito Comunista d’Italia). One of the views characterizing the faction was the belief that in the nations of established democratic rule-Western/Central Europe and the US-the parliament was no longer the site where important political and economic decisions were taken, an axiom drawn from the classical texts of Marxism. It had ceased to be a usable tribune from which to make known communist views, and for the longest period served to lead astray and dissipate revolutionary forces. Hence the parliament was to be opposed: with a democratic government, opposition to the bourgeois system was rendered most dramatically by boycotting political elections. A second tactic advanced by the Sinistra was the concept of “united front from below”: this meant avoiding the confusing political convergence of parties and organizations having disparate if not conflicting programs, while drawing all workers of whatever political, ideological or religious conviction into a common struggle for clear economic and social objectives and in defense of their conditions of life and work.

At the Second Congress of the Third International, the Sinistra played a determinant role in stiffening the conditions of admission. In so doing, at a time of continued and considerable social ferment, it hoped to bar admission to groups and parties whose acceptance of a revolutionary program and discipline would prove rhetorical and their actions detrimental, particularly if the postwar verve and revolutionary conditions receded, as was soon the case. In seeing the International as a true, authentic world party rather than a formal arithmetic summation of national parties, which later would be free to go on and “make politics” as each saw fit, of all the European communist groups the Sinistra was the clearest on the question of internationalism. Even as it was involved in founding a communist party in Italy, the Sinistra in the International stood for the reaffirmation of Marxism’s integrity and for an internationalism strategically and tactically binding the working classes of the West with the rebellious people of the East. It believed that a revolutionary communist party must seek the violent overthrow of the bourgeoisie leading to the establishment of the class dictatorship as a bridge to a classless society. Strongly favoring internal discipline, it maintained that, within both the national parties and the International, obedience must rest on the voluntary acceptance and understanding of the revolutionary program by each and every adherent, and not on bossy compulsion.

At the PSI’s 1921 Congress of Leighorn (Livorno), the Communist Sinistra broke away from the old reformist party and founded the Communist Party of Italy (PCd'I), a Section of the Communist International. Regardless of the subsequent assertions of a Stalinist historiography, the leading offices of the party were staffed entirely by Sinistra representatives and by Amadeo Bordiga. At this time, Gramsci and Palmiro Togliatti were in total agreement with this leadership. For two years, in a Western Europe where revolutionary elements were seeking a road to revolution to provide decisive aid to the USSR, the Sinistra-led CPI was the foremost edge of the politics of “Bolshevism, A Plant for Every Clime.” Amongst the trade unions, it carried out a strenuous campaign to construct a real united front-not of parties-of the working masses whatever their political loyalties; it fought no less strenuously against social-democratic reformism that misled the workers with its illusory pacifism and legalism; it openly confronted fascism, which it described as the reaction of industrial and agrarian capital to a worldwide economic crisis and the militancy of the proletariat, and not a feudal phenomenon as would be averred later by Stalinists; it built a defensive military apparatus against reaction and did not have to rely on such organizations as the “Arditi del Popolo”, a formation of spurious and uncertain nature; and during all those years marked by the reflux of the postwar revolutionary wave, the party maintained an international and internationalist stance, criticizing from the outset the rise of localism or autonomous actions and, above all else, the moves subordinating the International itself to Russian national needs.

After the arrest of Bordiga and a good many of the party’s leaders in early 1923–although they would be released by year’s end following a successful defense leading to acquittal-leadership passed to a secondary group more open to manipulation by the International. Despite a national conference of the party held in Como in May, 1924, at which the delegates voted overwhelmingly for the Sinistra, the party leadership was given by Moscow to a new Centrist grouping formed under Gramsci and Togliatti. The Sinistra was thus barred from leadership. The Centrists, employing means, methods and language correctly identified with Stalinism, in the course of the next two years crushed the Sinistra and its influence was largely eradicated: Prometeo, a journal speaking for the Sinistra, was suppressed after a few issues, party sections with Sinistra majorities were dissolved, Sinistra spokesmen were removed, their articles and views censured or not published, and the party put under a regimen of intimidation, suspicion, and discipline that was ever bossier and bureaucratic.

Archival evidence has shown that the III Party Congress, held outside Italy at Lyons, France, met before an assembly stacked by the Centrist leadership in various ways including:

in the pre-congressional congresses, the votes of absentee Sinistra followers were automatically given to the Gramscian Center; and

at a final meeting in Milan, delegates to Lyons were winnowed to eliminate Sinistra representation.

At that congress, the Sinistra was completely marginalized and no longer able to act or have its views known. At the VII meeting of the Enlarged Executive Committee of the Communist International held in Moscow between February and March of that year, Bordiga opposed “Bolshevization”, that is, the reorganization of the party on the basis of the factory cell that, under the pretense of increasing the workers’ influence, had the effect of enclosing the base within the narrowness of the factory or shop, to which the person of the functionary-bureaucrat became an indispensable source of “the line to be followed” and the embodiment of leadership. At that incandescently dramatic session of the VII Enlarged Executive Committee, Bordiga, who openly confronted and questioned Joseph Stalin, was the only delegate amongst all present to ask that the grave internal crisis extant within the Bolshevik Party-the prelude to the emergence of the faux and lying theory of “socialism in one country”- be posted as the order of the day for the next world congress. To quote his words: “the Russian Revolution is our revolution also, its problems our problems, and [therefore] every member of the revolutionary International has not only the right but also the duty to labor in its resolution.” Meanwhile, the Fascist authorities saw to it that Bordiga and the entire Italian Communist leadership were arrested long before the next world congress.

In the USSR, Stalin isolated the United Opposition. Between 1926 and 1930, the Sinistra followers were expelled from the party, and thus given over to Fascist repression or forced to emigrate. The campaign against the Sinistra was undertaken in parallel with the persecution of Trotsky and his supporters, although between the two currents there were dissimilarities of views-which did not prevent the Sinistra from defending Trotsky in the crucial years of 1927–1928. Bordiga himself was expelled in 1930 on the charge of “Trotskyism”. Meanwhile, first with the betrayal of the English General Strike in 1926 and then with the subordination of the Chinese Communist Party to the Kuomintang during the Chinese revolutionary year of 1927 resulting in the massacre of the Canton and Shanghai Communards by the Nationalists, Stalinism, a degenerative manifestation indicative of the rise of a bourgeois force within a USSR isolated by the absence of supportive working class revolution in the West, undertook the complete reversal of the principles of the communist program.[citation needed]

With Bordiga under continuous police surveillance and isolated in Naples, the Sinistra suppressed and hounded by Fascism and Stalinism, its members dispersed through emigration to the West where they had also to fight and oppose the growing illusions cast by bourgeois democracy, there began a phase of the history of the party which has been described as heroic by its militants afterwards. The Sinistra reorganized in France and Belgium under the name of the Faction Abroad (Frazione all'Estero) and published the periodicals Prometeo and Bilan, thus returning to the political battle. The situation was very difficult for this handful of scattered comrades. Theirs was a battle waged on three fronts: against Fascism, Stalinism, and bourgeois democracy. They continued the criticism of Moscow's policies-the "Popular fronts," the illusion about the efficacy of democracy, the continuous political somersaults that bewildered the working class, the Nazi–Soviet Pact, and Togliatti's appeal to "the brothers in black shirts." They worked vainly during the Spanish Civil War to get the uncertain left groups to orient themselves on a class basis. They carried on the struggle against Fascists and Nazis in occupied France, even spreading defeatism amongst German troops. With the myths of democracy penetrating ever deeper in the international workers movement, the Sinistra responded with critical analyses. At the onset of war in 1939, they pointed out its imperialistic character. It was already clear to them that Stalinism represented the worst of counterrevolutionary waves. With insufficient forces due to their isolation, they began the analysis of what happened in the USSR. It was this tenacious resistance, this determination to not allow a break in the "red thread" that led to the rebirth of the party in 1943.

In 1943, the Internationalist Communist Party was founded as Partito Comunista Internazionalista in Italy around Onorato Damen and Bruno Maffi. Hardened by prison, clandestinity and long years of militancy, all those men were ready to struggle to the end for the revolution, whose first strings they saw in the events of March 1943, then in the strikes in September in the North.

Struggling against the Partisans' war, and any enrolment of the workers under the banner of Italy or Togliatti, Partito Comunista Internazionalista waged a difficult, rigorously clandestine struggle, while being denounced by the PCI as "an agent of Germany and of fascism". An expectationally interesting document—the reports on the clandestine press sent to Benito Mussolini between 1943 and 1945—makes it possible to sweep away these accusations which were fabricated by the Stalinists:

"The only independent paper. Ideologically the most interesting and prepared. Against any compromise, defends a pure communism, undoubtedly Trotskyist, and thus anti-Stalinist. Declares itself without hesitation an adversary of Stalin's Russia, while proclaiming itself faithful to Lenin's Russia. Fights against the war in all aspects: democratic, fascist or Stalinist. Even struggles against 'the partisans', the Committee of National Liberation and the Italian Communist Party."

Although it is possible to see the errors of Mussolini's spies in declaring the Partito Comunista Internazionalista as Trotskyist where actual Trotskyists poured anti-German nationalism and gave full support to the 'partisan' war.

Partito Comunista Internazionalista developed rapidly amongst the workers, and by the end of 1944 it had formed several federations, the most important ones being in Turin, Milan and Parma. It developed its activity in the factories by forming "Internationalist Communist Factory Groups", advocating for the formation of workers' councils. The propaganda made by the party gained much support in the factories, especially among the workers who refused to go to war.

In 1944, after the American occupation of southern Italy, several groups claiming descend from the communist left were quickly formed and began to distribute their press illegally. In Naples a group called 'Frazione di Sinistra dei Communist e Socialisti' was formed around Bordiga, taking up the tradition of the Abstentionist Communist Fraction of 1919. The new fraction had a huge influence in this city and despite the presence of Togliatti and the Italian Communist Party centre, there were many PCI militants in southern Italy who, completely isolated from the 'centre' in exile, still held the positions of the left, and were not fully aware of the party's evolution. The term 'Frazione' adopted by Bordiga seemed to imply that they had not given up hope of winning over the militants of the PCI and PSI by eliminating their leaderships. This is why the Bordigist fraction did not constitute itself into a party before being absorbed by the Partito Comunista Internazionalista in 1945. The fraction managed to publish different papers in Naples, Salerno and Rome.

In December 1945, Partito Comunista Internazionalista held its first national conference in Turin, now as a strong party. Bordiga was absent from this conference, since he did not become a member of the party until 1949, although he made individuals contributions to it. In the congress, the hints about the future split in the Party appeared. Disagreements crystallized with Damen and Stefanini on one hand and Maffi and Bordiga's absent support on the other on the question of the function of the party, on the union question, and on the question of parties participation in elections.

Partito Comunista Internazionalista kept developing, particularly in Calabria, the party even had a huge influence on the agricultural proletariat and even on farmers. At this point, the party had grown very strong, having become virtually a mass party with 13 federations, 72 sections, numerous public meetings, its implantation in the main industrial centres, its factory press and so forth.

It was above all the question of parliamentarianism which precipitated the formation of tendencies in the Partito Comunista Internazionalista. The party had in fact put up candidates in the local elections in 1946 and national elections in 1948. Other divergences were grafted on to this one. On the one hand there was the Damen tendency advocating a voluntarist development of the 'party' and participation in elections, but opposed to any support for 'national liberation' movements; on the other hand, the Maffi tendency hostile to 'revolutionary parliamentarianism' and supported by Bordiga.

Bordiga's entrance to the party in 1949 was to precipitate the formation of opposition 'blocks'. For Bordiga, what was necessary was a return to Lenin and the theses of the Italian Left before 1926, which meant a rejection of Bilan's contributions on the national question, the unions and the transitional state. It was on all these questions and not on the question of elections which Damen in turn rejected, that the split took place between on one hand Maffi and Bordiga and on the other Damen and Stefanini. In 1952, it seemed that a majority followed Damen, who rejected any hope of conquering the unions and any support for national liberation.

In 1952, in Italy, there were two Partito Comunista Internazionalistas, both laying claim to Lenin and the Italian left. The party as led by Bordiga and Maffi soon started publishing Il Programma Comunista where the Damen splinter group held on to Prometeo and Battaglia Comunista.

The party (publishing Il Programma Comunista) took the name International Communist Party soon after the split and growing up rapidly on the international level.

Soon the International Communist Party had expanded and grew rapidly in several countries, and for a time became the main organization of the Communist Left tradition.

In 1964 a new split gave its birth based on its opposition towards Bordiga's thesis presented in party meeting in Florence, which tried to define new criteria built on organic centralism. This new split got named as Rivoluzione Comunista (RC) and made its critique of party's programmatism and proposed to intervent more actively in the class.

Until his death in 1970, Bordiga devoted himself to contributing to the enormous task of reconstructing the theoretical and political basis of the Party, which became truly international in fact as well as name in the 1960s. The "Fundamental Theses of the Party" (1951), "Considerations on the Organic Activity of the Party in a Situation which is Generally and Historically Unfavorable" (1965), "Theses on the Historic Duty, the Action and Structure of the World Communist Party" (1965), and "Supplementary Theses" (1966) gave the party its theoretical, political, and organizational structure.

In late 1973 the ICP underwent a serious split, which led to the orthodox militants (mostly based in Florence) reorganizing and moving forward, publishing Il Partito Comunista. The International Communist Party continues publishing in several languages, including the English press "Communist Left". Meanwhile, in 1982, the Il Programma ICP was decimated by further splits within their ranks, particularly in France and Italy. From one of these splits came a new organization under the ICP banner which publishes Il Comunista.

There have been several tendencies and organizations over the years which have more or less claimed their heritage to International (Italian) Communist Left or directly to the original International Communist Party. One of these tendencies, which started in 1981, is a group (expressly not a party) called 'n + 1' which publishes the review under same name and collects their volumes and booklet including articles and more detailed treatments of various subjects in the series "Quaderni Internazionalisti".

The International Communist Party holds that the doctrine of the party is founded on the principles of the historical materialism of the critical communism set out by Marx and Engels in the Communist Manifesto, Capital, and their other fundamental works and which formed the basis of the Communist International constituted in 1919 and of the Italian Communist Party founded at Leghorn in 1921 as a section of the Communist International and was a unitary and invariant body. The class party is accepted as the indispensable organ for the proletarian revolutionary struggle. It has always held that the party must historically get rid, once and for all, of the practice of alliances, even for transitory issues, with the middle class as well as with the pseudo-proletarian and reformist parties.

Holding that the Communist Party consists of the most advanced and resolute part of the proletariat, uniting the efforts of the working masses transforming their struggles for group interests and contingent issues into the general struggle for the revolutionary emancipation of the proletariat; the International Communist Party states that the duties of the party are propagating the revolutionary theory among the masses, organizing the material means of action, leading the working class all along its struggle, by securing the historical continuity and the international unity of the movement.

According to the International Communist Party, the party is not made up of all members of the proletariat or even of its majority. It is the organization of the minority which has, collectively, reached and mastered revolutionary tactics in theory and in practice; in other words, which sees clearly the general objectives of the historic movement of the proletariat in the whole world and for the whole of the historical course which separates the period of its formation from that of its final victory. The party is not formed on the basis of individual consciousness; the International Communist Party emphasizes that it is not possible for each worker to become conscious and still less to master the class doctrine in a cultural way, neither is this possible for each militant nor even for the leaders of the Party as individuals. To them, this consciousness lay in the organic unity of the Party. The Party is the organic tissue whose function inside the working class is to carry out its revolutionary task in all its aspects and in its successive phases.

Stressing the importance of the unity of the proletariat, the International Communist Party states that the party should never set up economic associations which exclude those workers who do not accept its principles and leadership. All forms of closed organizations that separate the working class are rejected. The ICP remains resolutely against the participation in the parliamentary elections, rejecting the idealist and utopian outlook which makes social transformation dependent on a circle of ”elected“ apostles and heroes.

The International Communist Party defines opportunism as a wave of degeneration of proletarian parties. In opposition to opportunism, it rejects the subordination of the party's action to that of political committees of fronts, coalitions or alliances even if this subordination was to restrict itself to public declarations and be compensated by internal instructions to militants or the party and by the subjective intentions of the leaders. It holds that in the West all alliances or proposals of alliances with social democratic or petit-bourgeois parties should be refused at all costs; in other words that there should be no united political front. According to the International Communist Party, what made the parties unable to foresee and face the opportunist danger was a fundamental deviation in principles: the party states that it was neither internal democracy nor free elections which give the Party its nature of being the most conscious fraction of the proletariat and its function of revolutionary guide. It is instead the matter of a deep discrepancy of conceptions about the deterministic organicity of the party as a historical body, living in the reality of the class struggle.

The principal activity today is accepted to be the re-establishment of the theory of Marxist communism by the International Communist Party. The party will bring forward no new theory, but reaffirm the full validity of the fundamental theses of revolutionary Marxism, amply confirmed by facts and falsified and betrayed by opportunism to cover up retreats and defeats. The International Communist Party denounces and defends combating the Stalinists as revisionists and opportunists just as it has always condemned all forms of bourgeois influence on the proletariat. Oral and written propaganda are seen as an important party action. The cult of the individual is rejected as a very dangerous aspect of opportunism which should be fought, while the Party retains complete autonomy from all other political groups, parties, formations and fronts.

Following a major split in 1973, the reorganized International Communist Party, sometimes called Florence section, began publishing their magazine, Il Partito Comunista, soon thereafter. in 1979 begun the publication of the theoretical review, Comunismo. Il Partito has sections in Italy, France, England, Spain, Germany and Venezuela, and publishes in several languages. The ICP's English periodicals are The Communist Left and The Communist Party.

Following an important split in 1973, this group continued publishing Il Programma Comunista. The organization underwent crippling splits in 1982. Beside Il Programma Comunista, it now publishes a journal in English (The Internationalist) and a journal in German (Kommunistisches Programm).

Following a final crippling explosion in 1982, the reorganized Partito Comunista Internazionale began publishing their magazine, Sul Filo Rosso del Tempo. The party is (probably only) located in Italy.

Il Bollettino is a group which existed only in Italy and published only in Italian. The organization was founded in 1982 and their magazine was regularly published for some years; it's unknown if this group is still active.